In March, an American graduate student and military veteran named Taylor Force was walking through the ancient Israeli port city of Jaffa when a knife-wielding Palestinian stabbed him to death and wounded 10 others.

On Monday, some four months after the deadly assault, the families of Force and four others whose relatives were killed or injured by Palestinians have filed a $1 billion lawsuit against Facebook, alleging that the popular social media site has “knowingly provided material support and resources” to the Palestinian terror group Hamas.

The lawsuit argues that Facebook has served as a platform for Hamas to incite violence and plan attacks, and has thus violated the Anti-Terrorism Act of 1992. That law prevents Americans from providing material support to militant groups like Hamas, which the U.S. and the European Union see as a terrorist organization. Hamas, which controls the Gaza Strip, has carried out attacks that have killed hundreds of Israeli citizens.

The four other victims whose families are represented in the case were dual Israeli-Americancitizens who were hurt or killed in terrorist attacks since 2014. Among the plaintiffs is the family of Yaakov Naftali Fraenkel, a 16-year-old whose abduction and killing led to a violent Israeli military incursion into Gaza, and three-month-old Chaya Braun, who died after a Palestinian rammed his car into a crowd at a train station in Jerusalem.

The lawsuit, which Israeli legal advocacy group Shurat HaDin filed with the U.S. District Court for the Southern District of New York, claims that Facebook “knowingly provided material support and resources to Hamas.” By doing so, the lawsuit says, the social media site facilitated the “terrorist group’s ability to communicate, recruit members, plan and carry out attacks, and strike fear in its enemies.”

Although the group that filed Monday’s lawsuit is independent from the Israeli government, officials in Jerusalem have long claimed that social media has fueled Palestinian violence against Israelis.

While attending a conference in Hungary last month, Israeli Justice Minister Ayelet Shaked said that social media sites, including Facebook and Twitter, were working to remove content that may incite violence.

“A joining of forces by justice ministers from all over the world against incitement and our joint work vis a vis the internet companies will lead to change,” she said in a post on her Facebook page. “Already now, the Israeli Justice Ministry is managing to remove pages, posts and inciteful sites by working with Facebook and Google.”

Hamas spokesman Sami Abu Zuhri responded to the lawsuit by telling Reuters that Israel was trying to turn Facebook against Palestinians although Israelis had “expressed pride at the killing of Palestinians” on the same site.

“The real test for the owners of Facebook is to reject this pressure,” he said.